RV Water Heater Pressure Relief Dripping
The Short Answer: An RV P&T that drips is almost never “a bad valve from the box.” City-water pressure over ~80 psi with no hose regulator, a tank filled solid then heated, or a seat that never reseated after someone lifted the lever. Typical relief is 150 psi / 210 °F — confirm the stamp. Never cap it. A stream is shut city and pump, kill energy, hire an RV tech.
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Search Intent & The Real Problem
You are on a pedestal. The little lever on the tank is wetting the bay. House-tank articles talk expansion tanks and 80-psi PRVs. Coaches often have neither. The 6- or 10-gallon is the expansion tank. Campground mains run 90–100 psi. You heat a completely full tank and the P&T becomes the fuse. Suburban and Atwood/Dometic valves look like miniature residential T&Ps and fail the same way after a “test.” Generic house overflow: T&P discharging. Bottom drips that are not the P&T: RV leaking from the bottom.
What other guides get wrong
They start with “replace the valve.” I have thrown away good P&Ts because nobody put a $15 regulator on the city hose. They tell you a dribble on first heat is normal forever. One recovery on a full tank can spit. A lifestyle of dripping is pressure. They lift the lever weekly “for maintenance” and then condemn the seat. And they cap it overnight so they can sleep. That is how a 6-gallon becomes an incident.
Step-by-Step Troubleshooting
Step 1: Prove it is the P&T, not the drain or the tank
| Wet location | What it is |
|---|---|
| Lever, discharge port, or the pipe off the P&T | This page |
| Drain plug / anode hex | Bottom leak |
| Jacket, burner tray, rust | Dead tank — shut LP |
| Bypass valves inside | Plumbing, not the P&T |
- What to look for: Dry the bay. Wait through one heat cycle. Water that returns only at the P&T is the valve or the pressure. Water that returns at the jacket is not a P&T page.
- Required tools: Paper towel, flashlight.
Read the stamp on the valve. Most RV units are 150 psi / 210 °F. A 75-psi valve on a city hose will weep all day and still be “working.”
Step 2: Gauge the city hose — this is the usual cause
- What to look for: Pressure at the city inlet. Over ~80 psi is too high for the coach and for the heater. No regulator, a regulator with a failed gauge, or a park that is running a fire-main. Pump-only dry camping: if it still drips, the tank was overfilled or the thermostat is stacked. Waterlogged house-style expansion tanks do not apply on most trailers — you are the expansion.
- Required tools: Hose-end regulator, a gauge.
Drop city pressure first. Replacing the P&T on a 100 psi pedestal is how you buy two valves.
Step 3: Fill level, heat cycle, and the lever someone lifted
- What to look for: Tank filled until it spat from the P&T, then electric or gas turned on — classic first-hour spit. After that, a dribble that dies is leftover expansion. A dribble that returns every recovery is still pressure or a thermostat running hot. Lever lifted to “test” or to drain faster: seat debris. Same physics as leaking after testing.
- Required tools: Patience through one cool-down. Do not keep cycling the lever.
Electric on with the tank empty after a long dump: ECO risk — Atwood electric, Suburban electric.
Step 4: Thermostat too hot vs a valve that will not reseat
- What to look for: Scalding water at the tap with a dripping P&T: thermostat or mixing problem, not “just pressure.” A valve that weeps with city off, pump off, and the tank cool is a dirty or failed seat — replace the P&T, do not cap it. A hard stream with energy on is shut down now — stuck open physics in a smaller tank.
- Required tools: Contact thermometer at a tap. City and pump off for the cool test.
Do not screw a cap on “until you get home.” Bypass the heater for the drive if you must. Leave the P&T open to atmosphere.
Step 5: Replace the valve — and only the valve — when the seat is done
- What to look for: Correct RV P&T, same pressure/temperature stamp, same thread. Tank spud that turns with the valve: stop, that is a heater. PTFE or dope on the threads per the valve sheet. Discharge aimed down and out of the bay, not at the burner. After install: regulator on the city hose before you fill.
- Required tools: Backup wrench on the tank, the matching valve. Shore power and LP off.
If the shell around the P&T is crusted or wet through the jacket, the tank is the leak. Valve swaps will not save it.
When DIY Ends: Calling a Licensed Pro
You may add a city-water regulator, stop lifting the lever, and photograph the stamp. Stop at a streaming valve, a spinning tank spud, a wet jacket, scalding discharge, or a propane smell. A licensed RV tech can swap a P&T without ovaling the opening. Same-day beats a capped valve and a ruptured 6-gallon in a rolling coach.
Frequently Asked Questions
Q: Why is the pressure relief valve dripping on my RV water heater? A: City water over about 80 psi, a completely full tank on first heat, or a seat that did not reseat after the lever was lifted. Put a regulator on the hose. Never cap the valve.
Q: Is it normal for an RV water heater relief valve to drip? A: A few spurts on the first heat cycle of a bone-full tank can happen. Dripping every recovery is pressure or a bad seat. A stream is an emergency.
Q: Can I cap the RV water heater pressure relief valve? A: No. Capping a P&T turns the tank into a bomb. Disconnect city water, kill the pump, and hire an RV tech if it will not stop.